Looking for another Earth right next door this week on planetary radio. Welcome to the Travel Show that takes you to the Final Frontier.

I'm Matt Kaplan at the Planetary Society.

Deborah Fisher wants to find an Earth-sized... I'm at Kaplan of the Planetary Society.

Deborah Fisher wants to find an Earth-sized planet in the habitable zone around the nearest

stars to our own, and she believes she has the right tool to do it.

She's back on our show to tell us how. Bill Nye has been

meeting Strange Bedfellows in the capital of the USA and Bruce Betts will tell us

how Mars and Mercury are becoming Bedfellows in the sky.

First though, let's go to the beach with Emily Lochuwala.

Emily, great to talk with you as usual,

especially when I think we're going to find

entire worlds in a grain of sand.

Yeah, I realized when I was talking to some people about the kinds of sediments that curiosity

has been observing on Mars that when I said the word sand, I meant something that people weren't

hearing because I'm a geologist and geologists have a very particular definition of what

sand means.

It's like the Eskimo words for snow. I saw on one of the charts in your blog at least five different kinds of sand.

That's right and the reasons that geologists are subdividing sand into all these different kinds with very special size fractions is because sediment behaves differently depending on the size of the grains.

The bigger the grain, the harder it is to move in a rushing stream.

The smaller the grain, the longer it takes to settle inside a lake.

It's very important actually for them to figure out what the size of the grains is that

curiosity is looking at. And the fact that a lot of the rocks that it's looking at has such coarse grains, things that are larger than grains of sand, they're actually technically called granules, means that it had to have been water that was moving the stuff around. It couldn't have been wind.

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